Current Issues and Perspectives of Algae in Drinking Water Supply System: Colloidal Algae Is an Important Noticed Existence Form

Algal blooms in water sources, exacerbated by global climate change and water eutrophication, pose a significant threat to water quality, ecological safety, and human health. Seasonal algae blooms in drinking water sources, particularly those in colloidal form, present substantial challenges to the safe and stable operation of drinking water treatment plants. To address these challenges and gain a better understanding, this study reviews current issues and perspectives on algae in the drinking water supply system (DWSS). Algal contaminations are more frequent and severe in the tropics and subtropics spatially, while temporally, they pose greater concern during summer and autumn. Moreover, various detection methods, including conventional and advanced techniques, are discussed based on the advantages and disadvantages in species identification, cell quantity, and morphology observation. Additionally, treatment processes in DWSS, particularly pre-oxidation and coagulation, are effective in removing most algae. Furthermore, judging from the characteristics, microalgae and Microcystis aeruginosa exist as colloidal algae among the whole process of DWSS, yet the physical states of algae have been largely overlooked in previous research. This study fills this gap by introducing colloidal algae as a distinct form and analyzing its detection and removal from a colloid science perspective. This review thus provides a new reference for targeted algae control in DWSS.